The field of the present invention is directed to exhaust systems for internal combustion engines and the equipment thereof.
Exhaust systems for internal combustion engines have recently required the addition of catalytic converters for many applications, particularly automobiles. The employment of such converters has resulted in increased requirements on the exhaust system to properly condition the exhaust prior to introduction to the converter. Of particular import is the maintenance of substantial heat in the exhaust gases such that effective conversion of polutants can be undertaken in the converter. Additionally, exhaust gas homogeneity is important to evenly distribute pollutants and gas flow through the catalyst. The even distribution of flow results in a minimum of back pressure. The even distribution of pollutants prevents hot spots resulting from a concentration of reacting pollutants, overloading of the catalyst preventing adequate conversion, and eventual blinding of the catalyst prematurely.
The principal solution to insuring homogeneity in both flow and mixture is to position the catalyst at some distance from the engine. However, additional attention must be directed to the design to insure maintenance of the appropriate temperature in the exhaust gases in such devices. Alternately, the catalyst may be placed close to the engine to insure proper heat maintenance. However, the proximity of the catalyst to the several exhaust passages from a multicylinder engine creates problems with gas flow and pollutant homogeneity to the catalyst and can also result in contamination of the engine by catalyst or catalytic converter particles drawn into the engine due to pulsation of the exhaust gases. Thus, in the situation where the catalytic converter is best placed close to the engine, a need exists for creating gas flow homogeneity, protection against catalytic particle injection into the engine and adequate heat maintenance.